local tdata = '{"ft":"s","f":"", "a":"gpio", "p":3,"time":{"untime":5, "msg":"111"}}'

t = cjson.decode(tdata)

print(type(t))
print(t["time"]["untime"])
t["time"]["untime"] = 1
print(t["time"]["untime"])
print(t["ft11111"])
print(nil and "true" or "false")